The method for recording by means of an ink-jet printer, a representative method among various color recordings, comprises generating ink droplets and depositing onto various recording materials (such as paper, film, cloth) for recording. The method has rapidly been spread in recent years and will be propagated in future because the said ink-jet printer is noiseless as its recording head does not touch a recording material, moreover, the said ink-jet printer can be easily downsized, works in a high-speed and gives easy color printing. The water-based ink dissolving a water-soluble dye in a water-based medium has been used as the ink for a fountain pen or a felt pen and ink-jet recording, wherein a water-soluble organic solvent is generally added for the medium so as to prevent ink from clogging at the pen nib or the ink-jet nozzle. The water-based ink is required to provide a satisfactory density of image, not to clog at the pen nib or the ink-jet nozzle, to dry quickly on the recording material, not to blur, and to have good storage stability. The provided image is also required to have satisfactory light fastness and water fastness. Black ink is the most important among various hues of inks prepared by various dyes because it is used for both a mono-colored image and a full-colored image. The dyes for the black ink have been disclosed by many applications (such as JP Laid-Open No. 144067/1980, JP Laid-Open No. 207660/1982, JP Laid-Open No. 147470/1983, JP Laid-Open No. 93766/1984, JP Laid-Open No. 190269/1987, JP Laid-Open No. 246975/1987, JP Laid-Open No. 22867/1988, JP Laid-Open No. 33484/1988, JP Laid-Open No. 93389/1989, JP Laid-Open No. 140270/1990, JP Laid-Open No. 167270/1991, JP Laid-Open No. 200852/1991, JP Laid-Open No. 359065/1992, JP Laid-Open No. 172668/1994, JP Laid-Open No. 248212/1994, JP Laid-Open No. 26160/1995, JP Laid-Open No. 268256/1995, JP Laid-Open No. 11076/2001, and JP Laid-Open No. 275383/2002). But there has not yet been provided any black ink to meet satisfactorily the above requirements in the market.
An ink-jet printer is widely used from a small OA printer to a big industrial printer. Therefore, better fastness such as the light fastness and the like in the inks for the said ink-jet printer are strongly required. However, there has not yet been provided any black ink to meet the requirements in spite of its highest demand. As for water fastness, it has been remarkably improved on the paper with the surface coated with inorganic fine particles, such as porous silica, alumina sol or a special ceramics, which can absorb the dye from ink, together with a cationic polymer or a PVA resin. However there are still many problems in light fastness and discoloration due to effects of ozone in air or the like on converted paper, so the better light fastness and the improvement of discoloration on various types of coated paper for the ink-jet printer are strongly required.
An azo type such as a diazo body, a triazo body or a tetrazo body is typical as a skeletal the chemical structure of a black colorant used in a water-based ink for ink-jet recording. But an azo type, though it has a relatively good water fastness, is inferior in light fastness compared to the cyan dye represented by a copper phthalocyanine. So, a water-based black ink is commonly obtained by combining several excellent performance colorants. However light fastness has not yet met the demand satisfactorily.
Therefore it is required to develop a black colorant having an excellent water fastness and light fastness, and suitable for inks for ink-jet recording in the absence of any other colorants. To meet the above requirements, a black phthalocyanine colorant obtained by carboxyethylation of aminophthalocyanine is disclosed by JP Laid-Open No. 11076/2001. The said colorant independently has a black hue and an excellent water fastness. However, once the rate of carboxyethylation is raised to improve the aqueous solubility, the said colorant becomes black slightly tinged with red, judging by the naked eye. So it is required to develop a black colorant having high aqueous solubility and also having a black hue no-tinged with red, preferably a black hue tined with blue.